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The ncmpi_bput_var<kind>_<type> family of functions is the buffered version of the nonblocking write functions ncmpi_iput_var<kind>_<type>.
The write data is buffered (cached) internally by PnetCDF and will be flushed to the file at the time of calling ncmpi_wait() or ncmpi_wait_all(). Unlike ncmpi_iput_var<kind>_<type>, once the call to this API returns, the caller is free to change the contents of write buffer.
<kind>: <none>, ’1’, ’a’, ’s’, or ’m’.
<type > for API names | <C type> for API arguments |
text | char |
schar | signed char |
short | short |
int | int |
float | float |
double | double |
uchar | unsigned char |
ushort | unsigned short |
uint | unsigned int |
longlong | long long |
ulonglong | unsigned longlong |
Prior to version 1.7.0, nonblocking APIs must be called while the netCDF file is in data mode. Starting from 1.7.0, nonblocking APIs can be called in either define or data mode. This API family can be called in either collective or independent data mode.
int ncmpi_buffer_attach (int ncid, MPI_Offset bufsize); int ncmpi_buffer_detach (int ncid); int ncmpi_bput_var_<type> (int ncid, int varid, const <C type> *buf, int *request); int ncmpi_bput_var1_<type> (int ncid, int varid, const MPI_Offset start[], const <C type> *buf, int *request); int ncmpi_bput_vara_<type> (int ncid, int varid, const MPI_Offset start[], const MPI_Offset count[], const <C type> *buf, int *request); int ncmpi_bput_vars_<type> (int ncid, int varid, const MPI_Offset start[], const MPI_Offset count[], const MPI_Offset stride[], const <C type> *buf, int *request); int ncmpi_bput_varm_<type> (int ncid, int varid, const MPI_Offset start[], const MPI_Offset count[], const MPI_Offset stride[], const MPI_Offset imap[], const <C type> *buf, int *request);
Flexible APIs:
int ncmpi_bput_var (int ncid, int varid, const void *buf, MPI_Offset bufcount, MPI_Datatype buftype, int *request); int ncmpi_bput_var1 (int ncid, int varid, const MPI_Offset start[], const void *buf, MPI_Offset bufcount, MPI_Datatype buftype, int *request); int ncmpi_bput_vara (int ncid, int varid, const MPI_Offset start[], const MPI_Offset count[], const void *buf, MPI_Offset bufcount, MPI_Datatype buftype, int *request); int ncmpi_bput_vars (int ncid, int varid, const MPI_Offset start[], const MPI_Offset count[], const MPI_Offset stride[], const void *buf, MPI_Offset bufcount, MPI_Datatype buftype, int *request); int ncmpi_bput_varm (int ncid, int varid, const MPI_Offset start[], const MPI_Offset count[], const MPI_Offset stride[], const MPI_Offset imap[], const void *buf, MPI_Offset bufcount, MPI_Datatype buftype, int *request);
ncid
NetCDF ID, from a previous call to ncmpi_open or ncmpi_create.
varid
Variable ID. Different MPI processes may use different variable IDs.
start
A vector of MPI_Offset integers specifying the index in the variable where the first of the data values will be written. The indices are relative to 0, so for example, the first data value of a variable would have index (0, 0, ... , 0). The elements of start correspond, in order, to the variable’s dimensions. Hence, if the variable is a record variable, the first index corresponds to the starting record number for writing the data values.
count
A vector of MPI_Offset integers specifying the number of indices selected along each dimension. To write a single value, for example, specify count as (1, 1, ... , 1). The elements of count correspond, in order, to the variable’s dimensions. Hence, if the variable is a record variable, the first element of count corresponds to a count of the number of records to write.
stride
A vector of MPI_Offset integers that specifies the sampling interval along each dimension of the netCDF variable. The elements of the stride vector correspond, in order, to the netCDF variable’s dimensions (stride[0] gives the sampling interval along the most slowly varying dimension of the netCDF variable). Sampling intervals are specified in type-independent units of elements (a value of 1 selects consecutive elements of the netCDF variable along the corresponding dimension, a value of 2 selects every other element, etc.). A NULL stride argument is treated as (1, 1, ... , 1).
imap
A vector of MPI_Offset integers that specifies the mapping between the dimensions of a netCDF variable and the in-memory structure of the internal data array. The elements of the index mapping vector correspond, in order, to the netCDF variable’s dimensions (imap[0] gives the distance between elements of the internal array corresponding to the most slowly varying dimension of the netCDF variable). Distances between elements are specified in type-independent units of elements (the distance between internal elements that occupy adjacent memory locations is 1 and not the element’s byte-length as in netCDF 2). A NULL argument means the memory-resident values have the same structure as the associated netCDF variable.
buf
Pointer to the location used for computing where the data values will be found; the data should be of the type appropriate for the function called. If the type of data values differs from the netCDF variable type, type conversion will occur.
bufcount
An integer indicates the number of MPI derived data type elements in the buf to be written to the file.
buftype
An MPI derived data type that describes the memory layout of buf. Starting from PnetCDF version 1.6.0, buftype can be MPI_DATATYPE_NULL. In this case, bufcount is ignored and the buf’s data type must match the type of the variable defined in the file - no data conversion will be done.
request
The nonblocking request ID returned by PnetCDF. It is to be used in a successive call to ncmpi_wait_all() or ncmpi_wait() for the completion of the nonblocking operation.
bufsize
The size of buffer users allow PnetCDF to allocate and use internally. The internal buffer will be used to aggregate multiple nonblocking buffered requests for better performance. The value can be different across processes.
ncmpi_bput_var<kind>_<type> returns the value NC_NOERR if no errors occurred. Otherwise, the returned status indicates an error. Possible causes of errors include:
Here is an example using ncmpi_bput_vara_double to add or change all the values of the variable named rh to 0.5 in an existing netCDF file named foo.nc. For simplicity in this example, we assume that we know that rh is dimensioned with time, lat, and lon, and that there are three time values, five lat values, and ten lon values.
#include <pnetcdf.h> ... #define TIMES 0 #define LATS 5 #define LONS 10 int status; /* error status */ int ncid; /* netCDF ID */ int rh_id; /* variable ID */ int request[2]; /* nonblocking request ID */ int st[2]; /* nonblocking request status */ MPI_Offset start[3] = {0, 0, 0}; /* start at first value */ MPI_Offset count[3] = {TIMES, LATS/2, LONS/2}; double rh_vals[LATS/2*LONS/2]; /* array to hold values */ int i; ... status = ncmpi_create(MPI_COMM_WORLD, "foo.nc", NC_CLOBBER | NC_64BIT_DATA, MPI_INFO_NULL, &ncid); if (status != NC_NOERR) handle_error(status); ... /* define dimensions and variable */ ... /* attach buffer */ status = ncmpi_buffer_attach(ncid, LATS*LONS*sizeof(double)); if (status != NC_NOERR) handle_error(status); /* write values into netCDF variable */ status = ncmpi_bput_vara_double(ncid, rh_id, start, count, rh_vals, &request[0]); if (status != NC_NOERR) handle_error(status); start[1] = LATS/2; start[2] = LONS/2; count[1] = LATS - LATS/2; count[2] = LONS - LONS/2; /* change contents of rh_vals[] */ status = ncmpi_bput_vara_double(ncid, rh_id, start, count, rh_vals, &request[1]); if (status != NC_NOERR) handle_error(status); status = ncmpi_wait_all(ncid, 2, request, st); if (status != NC_NOERR) handle_error(status); status = ncmpi_buffer_detach(ncid); if (status != NC_NOERR) handle_error(status);
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